Fourteen-year-old Lauren Hogg, who survived the Parkland, Florida, school shooting last week but lost four of her friends, rebuked first lady Melania Trump on Friday after Donald Trump Jr. "liked" tweets pushing conspiracy theories about the students.

Hogg's older brother, 17-year-old David Hogg, was the target of such tweets liked by Donald Trump Jr. earlier this week. The conspiracy theories allege Hogg, who has made powerful statements calling for bipartisan action on gun violence, is...